i) Field of the Invention
The present invention relates to communication in which connectionless communication and connection-oriented communication are combined for use, particularly to a packet processing apparatus and packet processing method in IEEE 1394 transfer system.
ii) Description of Related Art
In recent years, an IEEE 1394 interface relating to the present invention has spread as multimedia real-time transmission between digital, video, or audio and PC. An IEEE 1394 standard is defined as “IEEE Std 1394 IEEE Standard for a High Performance Serial Bus”, and in IEEE 1394 bus as a high-rate serial bus, data is divided in a packet form, and transmitted in a time division on the basis of a cycle of a length of 125 μs.
For a transmission method in the IEEE 1394, there are two methods of isochronous transmission and asynchronous transmission, and IEEE 1394 packet is transmitted as an isochronous packet and an asynchronous packet.
In the isochronous transmission, by securing a band necessary for transmission in all cycles, transmission in a fixed time is assured, an isochronous channel as communication connection is established beforehand between nodes to perform communication, and subsequently data transfer is performed in a connection-oriented communication system. Here, an identifier of the isochronous channel is called an isochronous channel number.
On the other hand, in the asynchronous transmission, in each cycle, arbitration is performed in a remaining time after the isochronous transmission, and the node having secured the bus performs data transfer. Different from the isochronous transmission, without establishing the connection beforehand, the identifier allotted univocally to the node on the bus is used to perform the data transmission in the connectionless communication system. Moreover, this identifier is called a node ID.
In this manner, the isochronous transmission corresponds to the connection-oriented communication in which a band is assured, and the asynchronous transmission corresponds to the connectionless communication in which no band is assured.
Such communication mode in which the IEEE 1394 interface is used is disclosed in the invention of Japanese Patent Application Laid-Open No. 234313/1999 relating to a multimedia exchange apparatus. The invention relates to the multimedia exchange apparatus for performing an exchange processing of communication, sound or image data, and using a high-rate serial bus of the IEEE 1394 interface standard to change a data transfer path by automatic allocation and perform the exchange processing. In this technique, various data in an inside line node apparatus and outside line node apparatus are automatically allocated to isochronous or asynchronous communication channels based on an identification code, and the like and packet transfer is performed.
In a conventional local area network (LAN), mainly Ethernet is used as a physical medium, but data transmission is the connectionless communication, and no band is assured in data transfer.
As the connection-oriented communication, ATM-LAN, and the like have been used in recent years, but all connections are established beforehand in a fixed manner between the nodes in LAN, and this disadvantageously results in remarkably laborious connection management. Moreover, when the connection is dynamically established by a signaling processing, processing overhead increases, and there is a disadvantage that a processing load in each terminal becomes heavy. For these reasons, the technique of ATM-LAN is more effectively used in the connection between LANs than within LAN.
As described above, the connection-oriented communication using ATM used in the conventional LAN and the connectionless communication represented by Ethernet are both provided with the aforementioned defects when used in LAN as they are.
On the other hand, the IEEE 1394 bus is a physical medium provided with both transfer systems of the connection-oriented and connectionless communications, and it is studied by a standardization organization or the like how to realize IP communication in the IEEE 1394 bus.
For example, with respect to Internet Protocol (IP) communication on IEEE 1394, there is a specification proposal of IP over IEEE 1394 by Internet Engineering Task Force (IETF). In this system, transmission is performed by encapsulating IP packet with an asynchronous packet, and this corresponds to the aforementioned connectionless communication.
Moreover, a method of connection-oriented communication for performing encapsulation and transmission with the isochronous packet is similarly proposed in IETF. However, both communications are provided with defects that no band is assured in the aforementioned connectionless communication, and the processing is heavy in the connection-oriented communication.